Each end of a railroad freight car typically includes two wheel and axle assemblies mounted between a pair of laterally spaced side frame members of a railcar truck. A laterally elongated bolster extends between and is supported by the side frames. A body of the railcar is supported on the bolster. Wheels are fit onto axles of each assembly to allow the railcar to ride over rails between locations. Toward the inner sides thereof, each wheel is provided with a radial flange which operably engages an inner side of the respective rail to inhibit excessive lateral displacement of the trucks thus keeping the trucks and railcar on the rails or tracks.
A typical railroad freight car further has a braking system including a brake beam assembly arranged in operable combination with each wheel and axle assembly on the car. Each brake beam assembly is provided with brake shoes for engaging the wheels to apply braking forces to the railcar. Each brake beam assembly is supported between the side frames of each truck to allow it to be operated into and out of braking positions in relation to the respective wheel and axle assembly. The opposed side frames each include guide brackets or pockets formed on an inner side of each side frame member. To support the brake beam assembly between the side frames, each brake beam assembly further includes an extension, extension lug, extension head, or paddle (hereinafter referred to as “guide member”) projecting outwardly from opposed ends of the brake beam formation and which are guidingly accommodated and received for reciprocal sliding movements within the guide brackets or pockets on the side frame members. Typically, wear liners are positioned within each guide bracket or pocket on the side frame to receive and slidably accommodate the respective guide member of the brake beam assembly therewithin.
One form of brake beam assembly commonly used in the railcar industry primarily includes a brake beam formation including compression and tension members joined to each other toward their ends where a brake head assembly is located and are separated at the middle by a fore-and-aft extending strut. It has been found beneficial for the brake beam formation to maintain both a degree of camber in the compression member and a degree or level of tension in the tension member. Each brake head assembly includes a brake head which carries a brake shoe thereon. The brake head assembly has a guide member arranged in operable association therewith. Moreover, the guide members extend in opposed direction relative to each other from the joined ends of the compression member and tension member.
The brake beam assemblies on the car are operated in simultaneous relation by a power source from a brake cylinder or hand brake and, through brake rigging, transmit and deliver braking forces to the brake shoes at the wheels of each wheel and axle assembly. On a typical railcar, the brake rigging, including a brake push rod, transmits forces, caused by the push of air entering the brake cylinder or the pull of the hand brake, to the brake shoes.
The brake rigging on the railcar, used to transmit and deliver braking forces to the brake shoes for each wheel, includes a multitude of linkages including various levers, rods and pins. For example, brake levers are used throughout the brake rigging on each car to transmit as well as increase or decrease the braking force directed to each wheel and axle assembly. The distance between various holes or openings on the brake levers determines the level of force transmitted to or between the various levers. Besides transferring force, the linkages of the brake rigging can also be used to change the direction of the force.
The strut on a conventional brake beam assembly defines an axially elongated slot which pivotally accommodates either a dead or a live lever. The levers are pivotally supported by the strut of the respective brake beam assembly. One end of the live truck lever is articulately connected to a longitudinally elongated top rod whose opposite end is connected to the cylinder lever of the railcar brake rigging. As is known, and besides being pivotally supported by the strut of the other brake beam assembly on the wheeled truck, the dead truck lever is articulately connected, intermediate the strut and the free end thereof, to the live truck lever. The free end of the dead truck lever is typically fulcrumed to the truck bolster or car body by a guide used to adjust the brakes.
To effectively lower the upper end of the brake lever relative to the position it would otherwise occupy if the brake lever were vertical, such brake levers are typically inclined or slanted lengthwise of the brake beam a certain number of degrees. That is, each brake lever, pivotally supported by the strut on each brake beam assembly, is inclined at an angle ranging between about 35 degrees and about 55 degrees relative to a horizontal plane.
The brake levers on each brake beam assembly are disposed to opposite sides of the bolster and are interconnected by a through rod or connecting rod. The live brake lever is also connected to the brake rigging. The most common through-rod rigging uses truck levers of unequal length. The live and dead levers have the same lever ratio, usually 2 to 1, which causes the through rod or connecting rod to ride at an angle to the longitudinal centerline of the railcar. As such, and during operation of the brake beam assemblies, the brake beam formations are forced to move laterally outward due to the lateral force component exerted thereon by the truck through rod. That is, and upon application of a braking force to the brake beam assembly, forces from the through rod to the live lever and dead lever has both a longitudinal and lateral components thereto. The lateral force applied to the brake beam assembly can be substantial especially when the braking force used to control the speed of the car is enhanced due to any number of forces acting on the car.
During operation, the side frames on each truck tend to shift with respect to one another. For example, when the railcar trucks are going around a bend, or when the commodity supported and carried by the car shifts or changes, the lateral distance between the side frames of each truck changes. The side frames can tend to shift inward, which causes the brake beam formation to be squeezed between the side frames of the truck. As such, the brake beam assembly is typically designed to yield a gap or clearance between the distal ends of the laterally spaced guide members on each brake beam assembly and the side frames to avoid having the brake beam assembly bind during operation.
Such gap or clearance, however, may be too wide is some situations, such as when the brake beam is off-center or kinked out of alignment. The aformentioned lateral movement or side thrust applied to the brake beam assembly can cause one of the brake shoes and the brake head to ride into contact with the wheel flange on one of the wheels which can result in wheel wear. Damage or wearing of the wheels on a railcar, for whatever reason, can result in significant repair expenses. Moreover, the aformentioned lateral movement or side thrust applied to the brake beam assembly can result in excessive wear and damage to the brake shoe and/or brake head while the mating shoe on the same brake beam assembly tends to ride on or overhang the outer edge of the opposed wheel. As used herein and throughout, the phrases or terms “overhang” or “overhanging” means and refers to either brake shoe laterally extending past an inner edge of the respective railcar wheel. Brake beam assemblies with unequal length brake levers commonly display wear patterns such as brake heads worn away by wheel flanges on diagonal corners of the wheel and axle assemblies. This leads to some wheels working harder to stop or control the speed of the car.
Besides serving to slidably support the brake beam assembly between the side frames and relative to the axis of the axle, the guide extensions or members operably associated with each brake beam assembly furthermore serve to establish a wear surface with each wear liner on the side frame. In these instances where the wear liner is fabricated from a metallic material, the guide member contact surfaces work with the wear liner to create smooth sliding surfaces whereby promoting reciprocatory movements of the brake beam assembly during operation. Of course, if the guide members on the brake beam assembly cannot smoothly ride within the wear liners, stress concentration are created and tend to hinder proper operation of the brake beam assembly.
Thus, there is a continuing need and desire for a railcar brake beam assembly designed to overcome the above-mentioned drawbacks and conditions mentioned above.